Is your main monitor (the one with the windows taskbar) the monitor on the right? If so, then you need to change your X co-ordinates for the left monitor windows to be negative numbers, that is, to the left of the left edge of your main monitor. Windows always counts the primary monitor (whether it's on the right or left) as the start point for X,Y calculations. In the non-standard setup where your main monitor is on the right you have to use negative X co-ordinates to position things on the left monitor.